I’m attending Costume Con because I love making costumes and want to learn more costumey skills. I’ll probably mostly wear street clothes to be comfortable during panels (and because I’m a little intimidated by the enormous costume-making skill that will surround me).

However, I do LOVE me some theme. I have one Spy-themed hall costume (which includes a couple store-bought items) and a nifty thrift store dress that I think would be fun for the Casino Royale Social. What’s the etiquette on this? I’m a little worried people will be critical of wearing store-bought items (or assume I made them). How much does this come up/matter outside of competing in the masquerades? Is it weird to wear a purchased outfit to a Costume Con social?

Outside of competition, everything is fair game. Attendees are expected to be everyone from first-timer newbs to uberMasters, so not everyone is expected to have the chops to whip out five new handmade hall costumes every con.

I mean hell, one of my hall costumes has purchased pants and shoes because GODDAMN I hate making pants. And they hate me.

__________________Founder and Vice-President, Madison Area Costuming Society, a chapter of the International Costumer's Guild

You'll see a little of everything. Purchased & vintage is perfectly fine for the halls - just be upfront about it. If you didn't make it - say so, most of us aren't that OCD. And if anyone turns up their nose about it, well... just come find me & I'll b*tch slap them for you. I can't stand that kind of snobbery!
In any case make sure to find me sometime during the weekend, hopefully Friday, I love meeting new people & re-meeting my "older" new friends.

I think this years social will see even more purchased stuff than in the past, just cause nice evening wear of a vintage style would go well, and to be honest, the con chair usually costumes that way, so it's all good

Don't worry about it. The first Costume Con I went to I wore several costumes that were made up of things I had bought and altered somewhat. Also two of my hall costumes for this year's con are also made up of bought pieces rather than being something I made myself. There's nothing at all wrong with it. No one will be bothered by it.